Automatic detection by a wearable camera

ABSTRACT

There is set forth herein a system including a camera device. In one embodiment the system is operative to perform image processing for detection of an event involving a human subject. There is set forth herein in one embodiment, a camera equipped system employed for fall detection.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application No.61/561,594 filed Nov. 18, 2011 entitled, “Automatic Fall Detection By AWearable Embedded Smart Camera.” The above application is incorporatedherein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The disclosed invention was made with government support under Grant No.CNS0834753 from the National Science Foundation. The government hasrights in this invention.

FIELD OF THE INVENTION

The present invention relates to imaging in general and specifically toan application that employs camera imaging.

BACKGROUND OF THE INVENTION

Falls in elderly patients are a major concern for both families andmedical professionals, as fall-induced injuries are the most commontypes of injuries and are now considered to be the eighth leading causeof death in adults aged 65 or older. The CDC reports that more thanone-third of U.S. adults aged 65 and over fall at least once each year.About 10% of all falls result in fractures, while a fifth of thereported cases require immediate medical attention. Untreated falls canresult in a number of adverse outcomes, from death due to cerebralhemorrhaging (for those taking blood thinner medications) to the loss ofmobility and depression from late treatment of fractures. For theelderly, medical examination and treatment after a fall is an extremelytime-sensitive matter, which is why fall detection is one of the moststudied methods of improving the safety of the older population,especially those living on their own.

Currently, there are a number of user-activated commercial devicesavailable on the market, where the user has to press a button to alertan emergency response center. The effectiveness of these devices,however, is limited by the ability of the patient to remain consciousafter a heavy fall.

About one-third of adults in the United States aged 65 or older fallevery year, with 20% of the reported fall cases needing prompt medicalattention. Although a number of approaches for detecting falls have beenproposed over the past few years, all of the methods have a trade-offbetween detection accuracy, processing power requirements, and the levelof intrusiveness.

SUMMARY OF THE INVENTION

There is set forth herein a system including a camera device. In oneembodiment the system is operative to perform image processing fordetection of an event involving a human subject. There is set forthherein in one embodiment, a camera equipped system employed for falldetection.

BRIEF DESCRIPTION OF THE DRAWINGS

The features described herein can be better understood with reference tothe drawings described below. The drawings are not necessarily to scale,emphasis instead generally being placed upon illustrating the principlesof the invention. In the drawings, like numerals are used to indicatelike parts throughout the various views.

FIG. 1 is a block diagram of system comprising a camera device.

FIG. 2 is a block diagram of a system comprising a camera device incommunication with an external processor equipped apparatus.

FIG. 3 illustrates a CITRIC camera: the wireless embedded smart cameraplatform used in the implementation.

FIG. 4 is an illustration of frame division into blocks and cells by theHOG algorithm.

FIG. 5 illustrates blocks and cells used in the implementation.

FIG. 6 illustrates dissimilarity correlation distances between the firstand current frame with no updating (top) and between the last andcurrent frame (bottom).

FIG. 7 illustrates views from an external reference of (a) sitting, (b)laying, and (c) falling, as well as the views from the fall detector ofthe same actions, respectively (d,e,f).

FIG. 8 illustrates various HOG block descriptors: (a) walking, (b)sitting, (c) laying, and (d) falling.

FIG. 9 illustrates event classification based on correlation distancelevels: (a) sitting, (b) laying, and (c) falling.

FIG. 10 is a block diagram of a camera device.

FIG. 11 is CITRIC camera: the wireless embedded smart camera platformused in the implementation.

FIG. 12 (a) Illustrates a of frame division into blocks and cells by theHOG algorithm; and FIG. 12 (b) illustrates blocks and cells used in theimplementation.

FIG. 13 illustrates correlation-based dissimilarity distances betweenthe current and key frame (top) and between the current and previousframe (bottom).

FIG. 14 illustrates views from an external camera of (a) sitting, (b)lying down, and (c) falling, as well as the views from the camera wornby the subject during the same actions (d,e,f), respectively.

FIG. 15 illustrates HOG block descriptors: (a) sitting, (b) lying down,and (c) falling.

FIG. 16 illustrates event classification based on correlation distancelevels: (a) sitting, (b) laying, and (c) falling.

FIG. 17 illustrates frame division into blocks and cells.

FIG. 18 illustrates false ‘fall’ alarm when using the original HOG.

FIG. 19 illustrates (a) False “fall” alarms are generated during lyingdown and sitting events when using the original HOG; (b) proposedapproach with fixed number of cells; (c) proposed approach with adaptivenumber of cells.

FIG. 20 illustrates Cells before and after a fall event.

FIG. 21 illustrates Histogram of Edge Orientations using a fixed numberof cells (a) before falling and (b) after falling. Employing adaptivenumber of cells (c) before falling and (d) after falling.

FIG. 22 (a) and (b) are photos taken of a subject to show two falltrials.

FIG. 23 are graphs as follows: Graphs of (a) DEO, (b) DES, (c) DEO×DES,and (d) (DEO×DES) 2 during events of falling, lying down and sitting;

FIG. 24 illustrates example frames captured by the camera during a fall.

FIG. 25 illustrates edge strength values corresponding to frames in (a)FIG. 8 a and (b) FIG. 8 c.

FIG. 26 illustrates example frames captured by the camera duringsitting.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 2, there is set forth herein an approachto detecting falls with a wearable wireless embedded smart camera(camera device) 100 that can have low power requirements. When a falloccurs, an appropriate message can be sent by a camera device 100 to anapparatus 200 at a location of an emergency response personnel, e.g.,via email, with an attached image captured using the subject's cameradevice 100. This image of the surroundings of camera device 100 aids inlocating the subject. As opposed to static camera devices that areinstalled in rooms to watch the subjects, a wearable camera device 100set forth herein in one embodiment does not point towards the subject,and thus, does not violate the subject's privacy. Moreover, since acamera device 100 set forth herein can be adapted to be wearable thesubject can be monitored wherever she/he may go including outdoors.

In addition, by using in one embodiment low-cost dedicated hardware inthe camera device 100, the cost of manufacturing such camera device 100is greatly decreased. A system 1000 set forth herein features theability to classify different scenarios, as well as features, usingHistogram of Oriented Gradients (HOG). In accordance with the HOGalgorithm, orientation features from an image can be extracted.

Although a system 1000 incorporating a camera device 100 set forthherein can be used for fall detection, a system 1000 set forth hereincan also detect and classify other human activities such as walking(which is considered default behavior), sitting, and laying down. Aclassification algorithm set forth herein can be based on adissimilarity correlation scheme. Input to the classification stage canbe derived from a normalized version of the extracted HOG features. Aclassification algorithm set forth herein uses the dissimilaritydistance as measurement index of the dissimilarity between two vectors.

There is set forth herein a system 1000 and method for detecting fallsusing a wearable embedded smart camera device 100, which in oneembodiment is a small, battery-operated unit. Privacy concerns can beaddressed with the disclosed system 1000. In one embodiment the cameradevice 100 can be worn by a subject, and the camera device 100 can beadapted so that data can be sent e.g. from device to apparatus 200, onlywhen a fall is detected as opposed to monitoring the subjectherself/himself 24/7. Captured frames captured with a camera device 100can be images of the surroundings, in one embodiment as well as imagesof the subject. A camera device 100 set forth herein can be adapted sothat when a fall occurs, an appropriate message can be sent by thecamera device 100 to emergency response personnel, e.g., via email, withan attached one or more image captured using the camera device 100. Inone embodiment, one or more image of the surroundings aids in locatingthe subject. As opposed to static cameras, that are installed in roomsto watch the subjects, a wearable camera device 100 set forth hereindoes not point towards the subject, and thus, does not violate thesubject's privacy. Moreover, since camera device 100 is wearable thesubject can be monitored wherever she/he may go including outdoors.

A system 1000 including a camera device 100 set forth herein can alsodifferentiate between actions of walking, sitting, laying down andfalling.

In one embodiment a system 1000 having a camera device 100 set forthherein can be adapted for use in statistics gathering and earlydiagnosis. A system 1000 having a camera device 100 can provide theinformation about how much time is spent in different rooms, and amountof activity. A decrease in activity, or increased amount of time spentin bed may be early signs of an illness.

As opposed to static cameras that are installed in rooms to watch thesubjects, a wearable camera device 100 set forth herein does not pointtowards the subject, and thus, can detect falls without violating thesubject's privacy. Moreover, since a camera device 100 set forth hereinis wearable the subject can be monitored wherever she/he may goincluding outdoors. In other words, the monitoring is not limited tospecific rooms or areas.

In one embodiment, a camera device 100 set forth herein can be adaptedfor capture of an image of the surroundings after a fall occurs. Thecamera device 100 can be adapted so that an image can be sent fromcamera device 100 to apparatus 200, e.g., via e-mail to emergencyresponders to easily locate the subject.

In addition, a system 1000 including a camera device 100 set forthherein can be adapted for use in statistics gathering and earlydiagnosis. A system 1000 having a camera device 100 set forth herein canbe adapted to provide information about how much time is spent indifferent rooms, and amount of activity. A decrease in activity, orincreased amount of time spent in bed may be early signs of an illness.

Various illustrative embodiments of the described apparatus and relatedapparatus and methods are set forth in the following Appendix. AppendixA of application No. 61/561,594: Automatic Fall Detection By a WearableEmbedded Smart Camera. Appendix A forms a part of the presentprovisional patent application. Appendix A of application No. 61/561,594is presented here.

In one embodiment as set forth herein a system 1000 set forth herein isprovided by a camera device (camera) 100. Camera device 100 in oneembodiment includes a processor provided by CPU 110 a memory 102 (e.g.,RAM and ROM), a tangible computer readable storage device 130 (e.g., amagnetic storage device of a hard drive, a flash memory device), animage sensor 150 coupled to system bus 180 via interface circuitry 160(e.g., control and DMA circuitry) and communication interface 170, e.g.,Ethernet, IEEE 802.11. In one embodiment, camera device 100 is providedby the CITRIC camera disclosed in Appendix A of application No.61/561,594. Appendix A of application No. 61/561,594 is presentedherein.

One or more program having instructions executable by a processor e.g.,by CPU 110 of camera device 100 for executing one or more of the imageprocessing algorithms (e.g. HOG) set forth herein including in AppendixA of application No. 61/561,594 can be stored on storage device 130 ofcamera device 100. Appendix A of application No. 61/561,594 is presentedherein. In one embodiment, image processing algorithms that are setforth herein are executed by CPU 110 of camera device 100.

In the embodiment of FIG. 2, system 1000 includes camera device 100 andan external processor equipped apparatus 200 having the elements of CPU110, memory 120, storage device 130, communication interface 170, andsystem bus 180 as set forth with reference to camera device 100. Cameradevice 100 and apparatus 200 can be in communication with one another,e.g., via a TCP/IP network.

In one embodiment, system 1000 can be adapted so that image data istransmitted from camera device 100 to external processor equippedapparatus 200 and further so that the transmitted image data isprocessed by a processor e.g., CPU 110 of the external processorequipped apparatus 200. The external processor equipped apparatus 200can be provided, e.g., by a personal computer at the location of theemergency response personnel as set forth herein (e.g., at a health carefacility remote from location of camera device 100). In one embodiment,one or more program having instructions executable by a processor e.g.,by CPU 110 of apparatus 200 for executing one or more of the imageprocessing algorithms (e.g., HOG) set forth herein including in AppendixA of U.S. provisional application No. 61/561,594 can be stored onstorage device 130 of apparatus 200. Appendix A of U.S. provisionalapplication No. 61/561,594 is presented herein. In one embodiment, imageprocessing algorithms that are set forth herein are executed by CPU 110of apparatus 200. Appendix A of U.S. provisional application No.61/561,594 is set forth herein below with minor formatting changesincluding reference numeral changes to avoid duplication.

[The following is an excerpt from Appendix A of U.S. provisionalapplication No. 61/561,594:]

Automatic Fall Detection by a Wearable Embedded Smart Camera.

About one-third of adults in the United States aged 65 or older fallevery year with 20% of the reported fall cases needing prompt medicalattention. Although a number of approaches for detecting falls have beenproposed over the past few years, all of the methods have a trade-offbetween detection accuracy, processing power requirements, and the levelof intrusiveness. This paper describes a novel approach to detectingfalls using Histograms of Oriented Gradients (HOG) for classifyingscenarios in an embedded wireless camera platform, which ispower-efficient and has low hardware requirements. Our device aims toeliminate privacy concerns by being worn by the subject and only sendingdata when a fall condition is detected, versus monitoring the subject24/7. In addition to detecting the fall, the camera has the ability todistinguish between the subject's “sitting” and “laying down”, as wellas capture and send images via email for easier location of the subjectby emergency response teams. The results demonstrated a low level offalse alarms and a 100% detection rate for falls.

Introduction

Falls in elderly patients are a major concern for both families andmedical professionals, as fall-induced injuries are the most commontypes of injuries and are now considered to be the eighth leading causeof death in adults aged 65 or older (M. Heron. Deaths: Leading causes2007. National Vital Statistics Reports, 59(8): 17, 21-22, August 2011).The CDC reports that more than one-third of U.S. adults aged 65 and overfall at least once each year (S. Lamb. Interventions for preventingfalls in older people living in the community: findings from therecently updated Cochraine Review. Parkinsonism & Related Disorders, 16,Supplement 1(0): S9, 2010. Abstracts of the 3^(rd) InternationalCongress on Gait & Mental Function and L. Larson and T. F. Bergmann.Taking on the fall: The etiology and prevention of falls in the elderly.Clinical Chiropractic, 11(3): 148-154, 2008). About 10% of all fallsresult in fractures, while a fifth of the reported cases requireimmediate medical attention (L. Gillespie, W. Gillespie, M. Robertson,S. Lamb, R. Cumming, and B. Rowe, Interventions for preventing falls inelderly people. Physiotherapy, 89(12):692-693, 2003). According to theU.S. census data, the number of elderly adults over 65 will rise to 20%by 2030 (from 12.9% in 2009), due to the increasing life expectancy anda dropping fertility rate (U.S. Department of Health and Human Services,Administration on Aging. A Profile of Older Americans. U.S. GovernmentPrinting Office, Washington, D.C., 2010 and W. Lutz, W. Sanderson, andS. Scherbov. The corning acceleration of global population ageing.Nature, 451(7179):716-9, 2008).

Untreated falls can result in a number of adverse outcomes, from deathdue to cerebral hemorrhaging (for those taking blood thinnermedications) to the loss of mobility and depression from late treatmentof fractures (J. Shelfer, D. Zapala, and L. Lundy. Fall risk, vestibularschwannoma, and anticoagulation therapy. Journal of the American Academyof Audiology, 19(3):237-45, 2008 and R. Voshaar, S. Banerjee, M. Horan,R. Baldwin, N. Pendleton, R. Proctor, N. Tuner, Y. Woodward, and A.Burns. Predictors of incident depression after hip fracture surgery. TheAmerican Journal of Geriatric Psychiatry, 15(9):807-14, 2007). For theelderly, medical examination and treatment after a fall is an extremelytime-sensitive matter, which is why fall detection is one of the moststudied methods of improving the safety of the older population,especially those living on their own. Currently, there are a number ofuser-activated commercial devices available on the market, where theuser has to press a button to alert an emergency response center. Theeffectiveness of these devices, however, is limited by the ability ofthe patient to remain conscious after a heavy fall.

A number of methods are currently being researched to autonomouslydetect falls. These methods can be grouped into the following threebroad categories, with some devices mixing the detection methods toachieve greater accuracy and a lower false-alarm rate (i.e.sensor-fusion) (S. Cagioni, G. Matrella, M. Mordonirii, F Sassi, and L.Ascari. Sensor fusion-oriented fall detection for assistive technologiesapplications. (In Proc. Ninth Int. Conf. Intelligent Systems Design andApplications ISM '09, pages 673-678, 2009).

Accelerometer/gyroscope-based detection: These devices are designed tobe wearable by the subject. The tilt and/or acceleration of the deviceis constantly monitored to detect unusual movement, which can then becharacterized as a fall condition (T. Tamara. Wearable accelerometer inclinical use. In Proc. 27th Annual Int. Conf. of the Engineering inMedicine and Biology Society IEEE-EMBS 2005, pages 7165-7166, 2005).There are also a number of methods for minimizing the false-positiverate of detection, such as a two-step approach that monitors for “nomovement” after the initial trigger (i.e. the person has fallen to thefloor and is unable to get up) (J. Zheng, G. Zhang, and T. Wu. Design ofautomatic fail detector for elderly based on triaxial accelerometer. InProc. 3rd Int. Conf. Bioinformatics and Biomedical Engineering ICBBE2009, pages 1-4, 2009 and T. Degen, H. Jaeckel, M. Rufer, and S. Wyss.SPEEDY: a fall detector in a wrist watch. In Proc. Seventh IEEE IntWearable Computers Symp, pages 184-187, 2003) and a statisticallytrained model based on the characteristics of a fall (X. Yang, A. Dinh,and L. Chen. A wearable real-time fall detector based on naive bayesclassifier. In Proc. 23^(rd) Canadian Conf. Electrical and ComputerEngineering (CCECE), pages 1-4, 2010). Some researchers have evencreated accelerometer-based fall detection software to run oncommonly-available hardware, such as Android smartphones to reduce theintrusiveness of the device into the daily life of the subject (F.Sposaro and G. Tyson. iFall: An android application for fall monitoringand response. In Proc. Annual Int. Conf of the IEEE Engineering inMedicine and Biology Society EMBC 2009, pages 6119-6122, 2009).

Static Camera-Based Detection:

In this approach, a stationary video camera constantly monitors thesubject and his or her surroundings to detect a fall condition. The vastmajority of the methods use raw video data, while others use eitherinfrared or contrast-detection to increase user privacy (Z. Fu, T.Delbruck, P. Lichtsteiner, and E. Culurciello, An address-event falldetector for assisted living applications. 2(2):88-96, 2008 and A.Sixsmith and N. Johnson. A smart sensor to detect the falls of theelderly. 3(2):42-47, 2004), effectively addressing concerns of potentialusers from a survey by Noury et al (N. Noury, A. Galay, J. Pasquier, andM. Ballussaud. Preliminary investigation into the use of autonomous falldetectors. In Proc. 30^(th) Annual Int. Conf of the IEEE Engineering inMedicine and Biology Society EMBS 2008, pages 2828-2831, 2008). Inaddition, there are a number of approaches that use efficient3D-reconstruction of images to detect falls more accurately (S.Zambanini, J. Machajdik, and M. Kampel. Detecting falls at homes using anetwork of low-resolution cameras. In Proc. 10th IEEE Int InformationTechnology and Applications in Biomedicine (ITAB) Conf, pages 1-4, 2010and P. Sicilian, A. Leone, G. Diraco, C. Distante, M. Maifatti, L.Gonzo, M. Grassi, A. Lombardi, G. Rescio, and P. Malcovati. A networkedmultisensor system for ambient assisted living application. In Proc. 3rdInt. Workshop Advances in sensors and Interfaces IWASI 2009, pages139-143, 2009).

Acoustic/Vibration-based detection: This solution is completelyinconspicuous and can be installed in any existing environment. Itusually consists or a number of sensor nodes, which detect thesound/vibrations and try to correlate them with normal activities andfalls. The one advantage to this type of system is that it can provide24/7 monitoring as well as eliminate patient compliance issues (F.Werner, J. Diermaier, S. Schmid, and P. Panek. Fall detection withdistributed floor-mounted accelerometers: An overview of the developmentand evaluation of a fall detection system within the project ehome. InProc. 5^(th) Int Pervasive Computing Technologies for Healthcare(CCECE), pages 1-4, 2010; M. Alwan, P. J. Rajendran, S. Kell, D. Mack,S. Dalal, M. Wolfe, and R. Felder. A smart and passive floor-vibrationbased fall detector for elderly. In Proc. 2^(nd) Information andCommunication Technologies ICTTA '06, volume 1, pages 1003-1007, 2006;and Y. Zigel, D. Litvak, and I. Gannot. A method for automatic falldetection of elderly people using floor vibrations and sound-proof ofconcept on human mimicking doll falls. 56(12):2858-2867, 2009).

This paper describes a novel approach to detecting falls with a wearablewireless embedded camera that has low power requirements. When a fallcondition occurs, an appropriate message is sent to the emergencyresponse personnel via email, with an attached image from the subject'scamera. This aids in locating the subject and does not violate thepatient's privacy on a constant basis. In addition, by using low-costdedicated hardware in the unit, the cost of manufacturing such units isgreatly decreased. The true novelty of the described approach comes fromthe ability to classify scenarios, versus just features (N. Dalal and B.Triggs, Histograms of oriented gradients for human detection. In Proc.IEEE, Computer Society Conf. Computer Vision and Pattern RecognitionCVPR 2005, volume 1, pages 886-893, 2005; Y. Said, M. Atri, and R.Tourki. Human detection based on integral histograms of orientedgradients and SVM. In Proc. Int Communications, Computing and ControlApplications (CCCA) Conf, pages 1-5, 2011; J. Baranda, V. Jeanne, and R.Braspenning Efficiency improvement of human body detection withhistograms of oriented gradients. In Proc. Second ACM/IEEE Int. Conf.Distributed Smart Cameras ICDSC 2008, pages 1-9, 2008), using Histogramsof Oriented Gradients.

Embedded Smart Camera Platform

The wireless embedded smart camera platform used in this implementationis a CITRIC mote (P. Chen, P. Ahammad, C. Boyer, S.-I. Huang, L. Lin, E.Lobaton, M. Meingast, S. Oh, S. Wang, P. Yan, A. Y. Yang, C. Yeo, L.-C.Chang, J. D. Tygar, and S. S. Sastiy. CITRIC: A low-bandwidth wirelesscamera network platform In Proc. Second ACM/IEEE Int. Conf. DistributedSmart Cameras ICDSC 2008, pages 1-10, 2008), which is shown in FIG. 3.The camera features a CMOS image sensor (OmniVision OV9655), a 624 MHzfixed-point microprocessor (PX A270), 64 MB SDRAM, and 16 MB NOR FLASH.A Crossbow TelosB mote is connected to the camera board to enablewireless communication, with a maximum data rate of 250 Kbps. The TelosButilizes a Texas Instruments M5P430 micro-controller and an IEEE802.15.4-compliant radio (Chipcon CC2420), which are components ofchoice due to their low-power operation.

Regarding FIG. 3, FIG. 3 illustrates a CITRIC camera: the wirelessembedded smart camera platform used in the implementation.

The low power requirements and small size of an embedded camera make itan ideal choice for a wearable fall detector.

Methodology

Histograms of Oriented Gradients (HOG) is a powerful image featureextraction algorithm introduced by Dalal and Triggs (N. Dalai and B.Triggs. Histograms of oriented gradients for human detection. In Proc.IEE Computer Society Conf. Computer Vision and Pattern Recognition CVPR2005, volume 1, pages 886-893, 2005). It is a lightweight algorithm thatrequires reduced computations, as compared to the state of the artfeature descriptors such as Haar wavelets, PCA-SIFT descriptors, andShape Contexts. Despite the algorithm being originally designed todetect human shapes (N. Dalai and B. Triggs. Histograms of orientedgradients for human detection. In Proc. IEEE Computer Society Conf.Computer Vision and Pattern Recognition CVPR 2005, volume 1, pages886-893, 2005), it has shown successful results in extracting featuresfrom a large variety of objects and it now serves as input for anyclassification algorithm. Since the algorithm does not require intensivecomputations, it is an ideal candidate for implementation on embeddedplatforms.

The main goal of the HOG algorithm is to compute and extract localizedfeatures in the form of histograms of edge orientations. Since thealgorithm, as described in (N. Dalai and B. Triggs. Histograms oforiented gradients for human detection. In Proc. IEEE Computer SocietyConf. Computer Vision and Pattern Recognition CVPR 2005, volume 1, pages886-893, 2005), divides the image into blocks and cells, it efficientlyexploits the spatial properties within the image by concatenating theedge orientations in a series of histograms, according to the number ofcells in a block. FIG. 4 illustrates the division of an image intoindividual blocks and cells.

Regarding FIG. 4, FIG. 4 is an illustration of frame division intoblocks and cells by the HOG algorithm.

The red squares in FIG. 4 represent blocks. Although, only two blocksare shown in the figure to make it less cluttered, the number of blocksand cells can be defined by the user and depends on the type ofapplication. Dalal and Triggs (N. Dalal and B. Triggs. Histograms oforiented gradients for human detection. In Proc. IEEE Computer SocietyConf. Computer Vision and Pattern Recognition CVPR 2005, volume 1, pages886-893, 2005) provide the optimal number of blocks to be used, followedby a detailed analysis on how the choices of blocks are made. The orangesquares in FIG. 4 represent the cells in a block, which is anapplication-dependent parameter.

Although there are many applications that use HOG to extract andclassify objects, our work introduces the HOG as a scene descriptor forhuman action analysis and classification. Consequently, as opposed tothe more common ways of using HOG theory that require a high number ofblocks and cells in order to classify objects, we have determined thatfor the classification of human actions, a reduced number of blocks andcells is required to accomplish the goal. FIG. 4 shows that if we arenot looking for a particular object with the size of a few cells, usinga large number of blocks and cells would unnecessarily compromise theefficiency of the algorithm. By simple observation, it is easy to seethat most of the cells in FIG. 4 will have a skewed distribution of edgeorientations. Thus, in our implementation, we decided to use 1 blockdivided into 9 cells as depicted in FIG. 5.

Regarding FIG. 5, FIG. 5 illustrates blocks and cells used in theimplementation.

The basic idea behind the HOG algorithm is the extraction of edgeorientation features from an image. For this purpose, the gradients inthe vertical and horizontal directions are computed within each cell inorder to obtain the phase information at each pixel's location. Once thephase information is obtained, it is grouped into 9-bin histograms witha rage from 0° to 180°. Every cell will produce an edge orientationhistogram and since there are 9 cells in a block, the HOG blockdescriptor is composed of 9 concatenated cell histograms. The HOG blockdescriptor is used for scene classification, as described in section 4.

Human Action Classification

The proposed system was designed for the fall detection of the elderly.In the event of a fall, the system triggers an emergency alarmrequesting help from an external rescue entity (e.g. a hospital, 9-1-1,family members). Although the system was designed mainly for falldetection, it can also detect and classify other human activities suchas walking (which is considered default behavior), sitting, and layingdown. There is set forth herein definitions for all human actions thatour device is able to detect, as well as provides the algorithm used inthe detection process. Additionally, experimental results in section 5.1demonstrate the robustness of the algorithm against false alarms.

The classification algorithm is based on a dissimilarity correlationscheme as described in (J. Szekely, M. L. Rizzo, and N. K. Bakirov.Measuring and testing dependence by correlation of distances. The Annalsof Statistics, 35(6)2769-2794, December 2007). Input to theclassification stage is derived from the normalized version of theextracted HOG features, as described in section 3. The classificationuses the dissimilarity distance as measurement index of thedissimilarity between two vectors. Thus, given a reference vector (R)and measurement vector (S) both with N components, the dissimilaritydistance is computed using equation 1. (1)

$\begin{matrix}{{{Drs} = {1 - \frac{\sum\limits_{i = 0}^{N - 1}\; {\left( {r_{i} - \overset{\_}{x}} \right)\left( {s_{i} - \overset{\_}{s}} \right)}}{\sqrt{\left\lbrack {\sum\limits_{i = 0}^{N - 1}\; {\left( {r_{i} - \overset{\_}{r}} \right)^{2}{\sum\limits_{i = o}^{N - 1}\; \left( {s_{i} - \overset{\_}{s}} \right)^{2}}}} \right\rbrack}}}}{{\overset{\_}{r} = {\sum\limits_{i = 0}^{N - 1}\; \left( r_{i} \right)}},{\overset{\_}{s} = {\sum\limits_{i = 0}^{N - 1}\; \left( s_{i} \right)}}}} & (1)\end{matrix}$

4.1. Dissimilarity Distance Comparison

In order to prevent false positives and distinguish between “falling”,“laying down”, and “sitting” conditions, two comparisons of thenormalized dissimilarity correlation distance (DCD) are made:

Current frame and “key frame” (DRS 1): initially, the “key frame” is setto be the first frame of the sequence. Whenever a fall condition occurs,the fall flag is set and the key frame is reset to the current frame.The fall flag remains set until the system detects that the subject hasgotten up. FIG. 6 (top plot) shows the DCD comparison between the firstand current frame, with no updating. As one can see, when the subjectfalls (frame 75, fall flag set) and subsequently gets up (at frame 175,fall flag unset), the DCD increases to 100 and then returns to zero. Inour experiment, the value of DRS1 is used to signal an event of somekind. Event classification is based the value of DRS2, outlined below.

Current frame and last frame (DRS2): the comparison between the currentand last frame allows this device to perform fall detection andmonitoring in a changing environment. When a fall is detected, there isa slight disturbance, after which the DCD reading returns to zero. Themagnitude of DRS2 allows us to classify the event as falling, layingdown, or sitting.

Regarding FIG. 6, FIG. 6 illustrates dissimilarity correlation distancesbetween the first and current frame with no updating (top) and betweenthe last and current frame (bottom).

Regarding FIG. 7, FIG. 7 illustrates views from an external reference of(a) sitting, (b) laying, and (c) falling, as well as the views from thefall detector of the same actions, respectively (d,e,f).

There is a strict set of logic, which governs when a certain condition(falling, sitting, or laying) has occurred. The values of DRS1 and DRS2have to be compared with threshold values (thldEvent, thldFall, andthldLay) in order to set the appropriate event flags. This logic can beseen in Algorithm 1. Once a fall is detected, a low-resolution image anda fall flag are transmitted.

Algorithm 1 (* Sets event flags based on detected conditions *)  1.fallCount ← 0  2. fallFlag ← 0, layFlag ← 0, sitFlag ← 0  3. whilefallCount < 2  4. if DRS1 = thldEvent  5. then if DRS2 > thldFall  6.then if fallFlag = 0 and   fallCount = 0  7. fallFlag ← 1  8. else iffallFlag = 1 and   fallCount = 1  9. then fallFlag ← 0 10. fallCount + + 11. else if DRS2 < thldFall and DRS2 > thldLay 12. thenlayFlag ← 1 13. else sitFlag ← 1

Evaluation

The experiments demonstrate the capabilities of the system of correctlydetecting and classifying common human activities such as walking,sitting, laying down and differentiating them from critical actions suchas a fall.

FIG. 7 shows the human activities to be classified. The top row, FIGS. 7(a-c) show the sitting, laying and falling events from an externalreference, while FIGS. 7 (e-f) in the bottom mw show the correspondingviews form the embedded smart camera worn by the subject.

As expected, the distortion presented in the embedded camera view inFIG. 7 (f) is larger than the distortion while sitting and laying, shownin FIGS. 7( d) 7(e), respectively. Therefore, the HOG block descriptorcalculated for the falling condition demonstrates a more evenlydistributed phase histogram pattern, which can be seen in FIG. 8 (d). Onthe other hand, sitting and laying present a relatively skewed histogrampattern which involves only a couple of bins in the histogram. The HOGblock descriptors for walking, sitting, laying, and falling arepresented in FIG. 8.

Regarding FIG. 8, FIG. 8 illustrates various HOG block descriptors: (a)walking, (b) sitting, (c) laying, and (d) falling.

Regarding FIG. 9, FIG. 9 illustrates event classification based oncorrelation distance levels: (a) sitting, (b) laying, and (c) falling.

Human Action Detection and Classification Experiments

FIGS. 9( a) and 9(b) show the dissimilarity correlation distances atevery captured frame. The logic for detecting and classifying humanactions described in this paper are outlined in section 4. According tothe logic, there are two main event threshold levels associated with theclassification tests, namely DRS1 and DRS2. DRS1 serves as a trigger forany event (i.e. sitting, laying, or falling), while the value of DRS2classifies the event or action according to the definitions for sitting,laying and falling introduced in section 4.

To declare a fall, both the DRS1 and DRs2 threshold levels have to bepassed. FIG. 9 (c) shows the outcome of a fall event. Both DRS1 and DRS2curves are plotted in blue and green, respectively. In contrast, sittingand laying do not exceed the DRS2 threshold level, despite the DRS1threshold levels being exceeded. This makes the system more robustagainst false alarms. Moreover, using the level of DRS2, the system candifferentiate between sitting and laying.

CONCLUSIONS

This paper introduces a novel approach for detecting and classifyinghuman activities using Histograms of Oriented Gradients (HOG). Thenovelty of our approach lies in the fact that we are able to detectscenarios using HOG, versus simply detecting objects, which has beendone in the past. Additionally, rather than monitoring a patient 24/7,we are able to infer human activities from the environment surroundingthe patient.

The entire approach was implemented in an embedded smart camera that isworn by the subject. Image features are computed in real-time fromframes captured by the smart camera. The main goal of this paper is todifferentiate falling events from normal human activities, such aswalking, sitting, and laying in bed. Successful results have beenpresented and the correct classification are shown. This approach uses adissimilarity distance correlator for distinguishing among differenthuman activities. The system captures and sends images via email foreasier location of the subject by emergency response teams.Experimentation yielded a low level of false alarms, and we were able todemonstrate a 100% detection rate for falls.

[End of Excerpt from Appendix A of U.S. provisional application No.61/561,594]

In connection with FIGS. 1 and 2 there is set forth hereinabove a cameradevice 100 which in one embodiment includes a processor provided by CPU110 a memory 102 (e.g., RAM and ROM), a tangible computer readablestorage device 130 (e.g., a magnetic storage device of a hard drive, aflash memory device), an image sensor 150 coupled to system bus 180 viainterface circuitry 160 (e.g., control and DMA circuitry) andcommunication interface 170, e.g., Ethernet, IEEE 802.11. In oneembodiment, camera device 100 is provided by the CITRIC camera disclosedin Appendix A of application No. 61/561,594. Appendix A of applicationNo. 61/561,594 is presented herein. There is also set forth hereinabovethat one or more program having instructions executable by a processore.g., by CPU 110 of camera device 100 for executing one or more of theimage processing algorithms (e.g. HOG) set forth herein including inAppendix A of application No. 61/561,594 can be stored on storage device130 of camera device 100. Appendix A of application No. 61/561,594 ispresented herein. In one embodiment, image processing algorithms thatare set forth herein are executed by CPU 110 of camera device 100.

According to aspects of an algorithm set forth in Appendix A ofapplication No. 61/561,594, there can be a comparison between a currentframe and a last frame (DRS2) which provides for fall detection. Thecomparison between the current and last frame allows the device toperform fall detection and monitoring in a changing environment. When afall is detected, there is a slight disturbance, after which the DCDreading returns to zero. The magnitude of DRS2 allows us to classify theevent as falling, laying down, or sitting. In addition there is setforth a comparison between a current frame and a key frame (DRS1).Current Initially, the “key frame” is set to be the first frame of thesequence. Whenever a fall condition occurs, the fall flag is set and thekey frame is reset to the current frame. According to aspects of analgorithm set forth in Appendix A of application No. 61/561,594, thevalues of DRS1 and DRS2 are compared with threshold values (thldEvent,thldFall, and thldLay) in order to set the appropriate event flags. Oncea fall is detected, a low-resolution image and a fall flag aretransmitted. Further there is set forth hereinabove that camera device100 can be worn by a subject, and the camera device 100 can be adaptedso that data can be sent e.g. from device to apparatus 200 (a processorequipped apparatus external from camera device 200), when a fall isdetected and further that camera device 100 can be adapted so that whena fall occurs, an appropriate message can be sent by the camera device100 to emergency response personnel, e.g., via email, with an attachedone or more image captured using the camera device 100. There is alsoset forth hereinabove that a camera device 100 set forth herein can beadapted for capture of an image of the surroundings after a fall occurs.The camera device 100 can be adapted so that an image can be sent fromcamera device 100 to apparatus 200, e.g., via e-mail to emergencyresponders to easily locate the subject.

Accordingly, based on at least the highlighted disclosure, there is setforth hereinabove a camera device comprising an image sensor; a memory;a processor for processing images; wherein the camera device is adaptedto be wearable by a human subject in a manner that images captured usingthe camera device represent surroundings of the human subject, whereinthe camera device is operative to process images captured using thecamera device for detection of a certain event, the certain event beingan action of the human subject, the certain event being detected byperformance of an image processing method that includes a comparison ofa subsequently captured image to an earlier captured image, and whereinthe camera device is operative to wirelessly transmit a message to anexternal destination responsively to the detection by the camera deviceof the certain event, e.g. wherein the camera device is operative towirelessly transmit a message to an external processor equippedapparatus responsively to the detection by the camera device of thecertain event.

In one embodiment as set forth hereinabove the camera device 100 can beworn by a subject, and the camera device 100 can be adapted so that datacan be sent e.g. from device to apparatus 200, only when a fall isdetected as opposed to monitoring the subject herself/himself 24/7.There is also set forth a camera device that aims to eliminate privacyconcerns by being worn by the subject and only sending data when a fallcondition is detected, versus monitoring the subject 24/7. Accordingly,there is set forth herein a camera device that is restricted fromtransmitting data, e.g. an image representing surroundings of a humansubject, data indicating a fall, unless a certain event is detected,e.g. a fall.

In another aspect there is set forth hereinabove in one embodiment awearable camera device 100 that does not point towards the subject, andthus, does not violate the subject's privacy. Moreover, since a cameradevice 100 set forth herein can be adapted to be wearable the subjectcan be monitored wherever she/he may go including outdoors. Withreference to FIG. 7 d, e and f of Appendix A of application No.61/561,594 there is illustrated exemplary views from a worn cameradevice illustrating that images captured using camera device 100 canrepresent surroundings of a human subject wearing the camera device 100.

Accordingly, based at least on the highlighted elements, there is setforth hereinabove a method comprising positioning a camera device on ahuman subject in a manner that the camera device is directed away fromthe human subject so that images captured using the camera devicerepresent surroundings of the human subject, the camera device having animage sensor, a memory and a processor, and processing images capturedusing the camera device to detect an occurrence of an event, the eventbeing an action of the human subject, the processing including comparinga subsequent captured image to a prior image.

There is set forth hereinabove that as opposed to static camera devicesthat are installed in rooms to watch the subjects, a wearable cameradevice 100 set forth herein in one embodiment does not point towards thesubject, and thus, does not violate the subject's privacy. Moreover,since a camera device 100 set forth herein can be adapted to be wearablethe subject can be monitored wherever she/he may go including outdoors.Accordingly, there is set forth hereinabove processing by a cameradevice 100 wherein the processing includes processing of images whereinthe images are devoid of a representation of a human subject on whichthe camera device is positioned. There is also accordingly set forthhereinabove processing by a camera device 100 wherein the processingincludes processing of images captured while the human subject isinternal of a building and processing of images captured while the humansubject is external of a building.

In another aspect, there is set forth hereinabove one or more programhaving instructions executable by a processor e.g., by CPU 110 of cameradevice 100 for executing one or more of the image processing algorithms(e.g. HOG) set forth herein including in Appendix A of application No.61/561,594 can be stored on storage device 130 of camera device 100.Appendix A of application No. 61/561,594 is presented herein. In oneembodiment, image processing algorithms that are set forth herein areexecuted by CPU 110 of camera device 100.

Accordingly, based at least on the highlighted elements there is setforth hereinabove a computer program product for detecting action of ahuman subject, the computer program product comprising: a computerreadable storage medium readable by a processing circuit and storinginstructions for execution by the processing circuit for performing amethod comprising: processing, by a processor, images representingsurroundings of a human subject; determining, by the processor,responsively to the processing an action of the human subject, whereinthe processing includes comparing a subsequently captured image to aprior captured image.

In one aspect system 1000 can be operative so that an image processingrate at which frames captured by camera device 100 are subject to imageprocessing is restricted from being slower than a frame rate of cameradevice 100. In one example, a frame rate of camera device 100 is 15frames per second and an image processing rate of CPU 110 of cameradevice 100 for performance of image processing methods set forth herein,e.g. for updating the running calculations herein per each frame isrestricted from being slower than 15 frames per second. In such manner,it is assured that each frame of a succession of frames will be subjectto processing, thus reducing a likelihood of an event being missed. Inorder to speed up an image processing rate various methods can beimplemented. For example an appropriately configured FPGA can beutilized for performance of edge detection. Lower resolution images canbe captured and/or processed and methods can be employed for locatingregions of interest within processed images.

In one example the image processing rate is restricted from being lessthan 50% of the speed of the frame rate, e.g. is restricted from beingless than 7.5 frames per second where the frame rate is 15 frames persecond. In one example, the image processing rate is restricted frombeing less than 10 frames per second where the frame rate is 15 framesper second. In one example, the processing rate of CPU 110 of cameradevice 100 is restricted from being slower than 5 frames per second. Tothe extent that an image processing rate is maintained at a rateproximate to the frame rate, a number of frames not available forprocessing (the number of “skipped” frames not subject to processing)will not negatively impact a capacity of system 1000 to detect an event.In the development of system 1000, it was determined that maintaining animage processing rate of at least 5 frames per second will provide forreliable detection of an event. In one example, the image processingrate is restricted from being slower than 10 frames per second. In oneexample, the image processing rate is restricted from being slower than15 frames per second.

It has been set forth herein, in one aspect, that the classification ofevents performed by system 1000 can include a classification of an eventas a laying down event. System 1000 can also be employed for detectionof a termination of an event, e.g. with description of the “fall flagunset” in Appendix A of U.S. Patent Application No. 61/561,594 presentedherein. As has been set forth herein an action of a human subject toterminate an event will result in a change in the value DSR1. In oneaspect, there is set forth herein one or more program havinginstructions executable by a processor e.g., by CPU 110 of camera device100 for determining whether a human subject has become ill. In oneexample, the processing can be based on a duration of a laying event.For example, a “has become ill” event can be declared responsively to aduration of a laying down event exceeding a threshold. The threshold towhich a duration of a falling down event can be compared can be apredetermined threshold or a variable threshold variable based on one ormore control input. In one example, the threshold can be establishedbased on an average duration of a laying down for the human subject. Inone example the threshold can be established at 150% of the averageduration of a laying down event for the human subject. One or moreprogram having instructions executable by a processor e.g., by CPU 110of camera device 100 for executing one or more of the image processingalgorithms forth herein including image processing algorithms forperforming a method wherein illness of a human subject can be detectedresponsively to image processing can be stored on storage device 130 ofcamera device 100. In one embodiment, image processing algorithms thatare set forth herein are executed by CPU 110 of camera device 100.

In one example, the determination of a “becoming ill” event can be basedin the alternative or in addition on a number of laying down events pera defined time period. For example, a laying down event can be declaredresponsively to a count of (a number of) laying down events exceeding athreshold within a predetermined time window. For example, a “has becomeill” event can be declared responsively to duration of a laying downevent exceeding a threshold. The threshold to which a count of fallingdown event can be compared can be a predetermined threshold or avariable threshold variable based on one or more control input. In oneexample, the threshold can be established based on an average count of alaying down for the human subject per a predetermined time period, e.g.per day. In one example, the threshold can be established at 150% of theaverage count of laying down event for the human subject per day. It hasbeen described that a determination that a human subject has become illcan be made responsively to one or more of a duration and count oflaying down events. The determination of a human subject becoming ill inthe alternative or in addition can be made responsively to one or moreof a duration and count of sitting down events (in one example, adetermination that a human subject has become ill can be responsive toan increase in a duration or count of sitting events). One or moreprogram having instructions executable by a processor e.g., by CPU 110of camera device 100 for executing one or more of the image processingalgorithms forth herein including image processing algorithms forperforming a method wherein illness of a human subject can be detectedresponsively to image processing can be stored on storage device 130 ofcamera device 100. In one embodiment, image processing algorithms thatare set forth herein are executed by CPU 110 of camera device 100.

In one aspect there is set forth herein one or more programs havinginstructions executable by a processor e.g., by CPU 110 of camera device100 for determining whether a human subject has become ill byperformance of a method set forth herein and further for transmitting amessage to an external processor equipped apparatus, e.g. apparatus 200responsively to a determination that a human subject has become ill. Thetransmitted message can include an indication that a human subjectwearing camera device 100 has become ill. The transmitted message caninclude an image of the surroundings of the human subject. Such imagecan facilitate a location of the human subject. As set forth herein, theimage can be devoid of a representation of the human subject so that aprivacy of the human subject is maintained. One or more program havinginstructions executable by a processor e.g., by CPU 110 of camera device100 for executing one or more of the image processing algorithms forthherein including image processing algorithms for performing a methodwherein illness of a human subject can be detected responsively to imageprocessing can be stored on storage device 130 of camera device 100. Inone embodiment, image processing algorithms that are set forth hereinare executed by CPU 110 of camera device 100.

In one aspect, there is set forth herein one or more program havinginstructions executable by a processor e.g., by CPU 110 of camera device100 for performance of a method including outputting an indicatorobservable by a human subject wearing camera device 100 responsively toimage processing, e.g. performed by CPU 110 of camera device 100. Theindicator can be one or more of visible, audible and tactile. As setforth in FIG. 10 camera device 100 in addition to the elements set forthin FIG. 10 can include an output unit 190 which can be connected tosystem bus 180. Output unit 190 can include one or more output device,e.g. a display, an audio output device (a speaker), a tactile outputdevice (e.g. vibration output device). In one example, camera device 100can be operative to output an indicator using output unit responsivelyto one or more event detected for a human subject wearing camera device100. One or more program having instructions executable by a processore.g., by CPU 110 of camera device 100 for executing one or more of theimage processing algorithms forth herein including image processingalgorithms for performing a method wherein an indicator observable by ahuman subject wearing camera device 100 is output responsively to imageprocessing can be stored on storage device 130 of camera device 100. Inone embodiment, image processing algorithms that are set forth hereinare executed by CPU 110 of camera device 100. Features set forth hereincan be combined. For example a transmittal of a message to an externalprocessor equipped apparatus can be accompanied by an output of anindicator observable by a human subject wearing camera device 100.

In one example, camera device 100 can be operative to monitor forinactivity of a human subject and can output indicators to promptincreased activity level of a human subject responsive to a detection ofinsufficient activity. In one example, in response to one or more of aduration or count of a detected laying down event exceeding a threshold,camera device 100 can output an indicator in the form of one or more ofa displayed prompt to “get up” or “begin walk”, an audio prompt to “getup” or “begin walk” or a tactile (e.g. vibrational) prompt to increaseactivity level. In one embodiment, such output indicators can be outputresponsively to a determination that a human subject has become ill aspreviously set forth herein. In one example, in response to one or moreof a duration or count of a detected sitting down event exceeding athreshold, camera device 100 can output an indicator in the form of oneor more of a displayed prompt to “get up” or “begin walk”, an audioprompt to “get up” or “begin walk” or a tactile (e.g. vibrational)prompt to increase activity level. One or more program havinginstructions executable by a processor e.g., by CPU 110 of camera device100 for executing one or more of the image processing algorithms forthherein including image processing algorithms for performing a methodwherein an indicator observable by a human subject wearing camera device100 is output responsively to image processing can be stored on storagedevice 130 of camera device 100. In one embodiment, image processingalgorithms that are set forth herein are executed by CPU 110 of cameradevice 100.

In one example, camera device 100 can be operative to monitor foractivity of a human subject and can output indicators to promptdecreased activity level of a human subject responsively to adetermination of unwanted activity (that the activity of the humansubject has exceeded a desirable level). In some instances it may bedesirable that an activity level of a human subject be decreased, e.g.where the human subject has a heart condition or otherwise requiresrest, the human subject is a flight risk, the human subject otherwisetends to exhibit unwanted motion. In one example, in response to one ormore of a duration or count of a detected laying down event failing toexceed a threshold, camera device 100 can output an indicator in theform of one or more of (a) a displayed prompt prompting to stop currentactivity to thereby decrease a current activity level, e.g. a displayedprompt “lay down”, (b) an audio prompt prompting to stop currentactivity to thereby decrease a current activity level, e.g. an audioprompt to “lay down” or (c) a tactile (e.g. vibrational) promptprompting to stop a current activity to thereby decrease a currentactivity level. In one example, in response to one or more of a durationor count of a detected sitting down event failing to exceed a threshold,camera device 100 can output an indicator in the form of one or more of(a) a displayed prompt prompting to stop current activity to therebydecrease a current activity level, e.g. a displayed prompt “sit down”,(b) an audio prompt prompting to stop current activity to therebydecrease a current activity level, e.g. an audio prompt to “sit down” or(c) a tactile (e.g. vibrational) prompt prompting to stop a currentactivity to thereby decrease a current activity level. One or moreprogram having instructions executable by a processor e.g., by CPU 110of camera device 100 for executing one or more of the image processingalgorithms forth herein including image processing algorithms forperforming a method wherein an indicator observable by a human subjectwearing camera device 100 is output responsively to image processing canbe stored on storage device 130 of camera device 100. In one embodiment,image processing algorithms that are set forth herein are executed byCPU 110 of camera device 100. There is set forth herein a computerprogram product for detecting action of a human subject, the computerprogram product comprising: a computer readable storage medium readableby a processing circuit and storing instructions for execution by theprocessing circuit for performing a method comprising: processing, by aprocessor, images representing surroundings of a human subject;determining, by the processor, responsively to the processing an actionof the human subject, wherein the processing includes comparing asubsequently captured image to a prior captured image, and wherein themethod includes one or more of transmitting a message to an externalprocessor equipped apparatus responsively to the determining andoutputting an indicator observable by the human subject responsively tothe determining.

Additional aspects and embodiments of systems apparatus and methods setforth herein are set forth in Example 1 and Example 2 below. Imageprocessing algorithms set forth in Examples 1 and 2 in one embodimentare executed by CPU 110 of camera device 100. One or more program havinginstructions executable by a processor e.g., by CPU 110 of camera device100 for executing one or more of the image processing algorithms forthherein including the image processing algorithms set forth in Example 1and Example 2 can be stored on storage device 130 of camera device 100.

Example 1

About one-third of adults in the United States aged 65 or older fallevery year with 20% of the reported fall cases needing prompt medicalattention. Although a number of approaches for detecting falls have beenproposed over the past few years, these methods have a trade-off betweendetection accuracy, coverage area, processing power requirements, andthe level of intrusiveness. This paper describes a novel method fordetecting falls by using a wearable embedded smart camera, which is asmall, battery-operated unit with low power requirements. The proposedapproach employs Histograms of Oriented Gradients to detect falls aswell as classify scenarios on an embedded wireless smart cameraplatform. Our approach to fall detection also aims to eliminate privacyconcerns. The camera is worn by the subject, as opposed to monitoringthe subject. Hence, the captured frames are the images of thesurroundings, and not of the subject. Moreover, since the camera iswearable, the subject can be monitored wherever she/he may go includingoutdoors. Data is transmitted only when a fall condition is detected. Inaddition to detecting falls, the camera has the ability to distinguishbetween the actions of “sitting” and “lying down”, as well as to captureand send images of the surroundings wirelessly for easier localizationof the subject by emergency response teams. The experimental results arevery promising with a 96.15% detection rate for falls.

Falls of elderly patients are major concern for both families andmedical professionals, since fall-induced injuries are the most commontypes of injuries and are now considered to be the eighth leading causeof death in adults aged 65 or older. The CDC reports that more thanone-third of U.S. adults aged 65 and over fall at least once each year.About 10% of falls result in fractures, while a fifth of the reportedcases require immediate medical attention. According to the U.S. censusdata, the number of elderly adults over 65 will rise to 20% by 2030(from 12.9% in 2009), due to increasing life expectancy and a droppingfertility rate.

Untreated falls can result in a number of adverse out-comes, from deathdue to cerebral hemorrhaging (for those taking blood thinnermedications) to the loss of mobility and depression from late treatmentof fractures. For the elderly, medical examination and treatment after afall is an extremely time-sensitive matter, which is why fall detectionis one of the most studied methods of improving the safety of the olderpopulation, especially those living on their own. Currently, there are anumber of user-activated commercial devices available on the market,where the user has to press a button to alert an emergency responsecenter. The effectiveness of these devices, however, is limited by theability of the patient to remain conscious after a heavy fall.

A number of methods are currently being researched to autonomouslydetect falls. These methods can be grouped into the following threebroad categories, with some devices mixing the detection methods toachieve greater accuracy (i.e. sensor-fusion):

Accelerometer/gyroscope-based detection: These devices are designed tobe wearable by the subject. The tilt and/or acceleration of the deviceis monitored to detect unusual movement, which can then be characterizedas a fall condition. There are also a number of methods for decreasingthe false-positive rate, such as a two-step approach that monitors for“no movement” after the initial trigger (i.e. the person has fallen tothe floor and is unable to get up) and a statistically trained modelbased on the characteristics of a fall. Some researchers haveimplemented accelerometer-based fall detection software to run oncommonly-available hardware, such as Android smart-phones to reduce theintrusiveness of the device.

Static camera-based detection: In this approach, a stationary cameraconstantly monitors the subject and his or her surroundings to detect afall event. The vast majority of the methods use raw video data, whileothers use either infrared or contrast-detection to increase userprivacy, addressing concerns of potential users from a survey by Nouryet al. In addition, there are a number of approaches that use3D-reconstruction to detect falls.

Acoustic/Vibration-based detection: This solution is completelyinconspicuous and can be installed in any existing environment. Itusually consists of a number of sensor nodes, which detect thesound/vibrations and try to correlate them with normal activities andfalls. The one advantage to this type of system is that it can provide24/7 monitoring as well as eliminate patient compliance issues.

Yet, both the static-camera based and acoustic/vibration basedapproaches will be limited to the areas where the sensors are installed.This paper describes a novel method for detecting falls by using awearable wireless embedded smart camera that is a small,battery-operated unit with low power requirements. Our approach to falldetection also aims to eliminate privacy concerns. As opposed to staticcameras, that are installed in rooms to watch the subjects, thiswearable smart camera does not point towards the subject. Hence, thecaptured frames are the images of the surroundings, not of the subject,and do not violate the subject's privacy. Moreover, data or messages aretransmitted only when a fall is detected. In case of a fall, anappropriate message can be sent wirelessly to the emergency responsepersonnel, including an image from the subject's camera. This image ofthe surroundings aids in locating the subject. In addition, since thecamera is wearable, the subject can be monitored wherever she/he may goincluding outdoors. Thus, contrary to other static sensor-basedapproaches, fall detection is not limited to areas where the sensors areinstalled. By using low-cost dedicated hardware, the cost ofmanufacturing such units is greatly decreased.

The approach set forth herein employs Histograms of Oriented Gradients(HOG) to detect falls. In addition, the camera has the ability todistinguish between the actions of “sitting”, “lying down” and“falling”. One of the novelties of the described approach is the abilityto classify scenarios, versus just features by using HOG.

An embedded smart camera platform can be utilized. The wireless embeddedsmart camera platform used in this implementation is a CITRIC mote,which is shown in FIG. 11. The embedded camera features a CMOS imagesensor (OmniVision OV9655), a 624 MHz fixed-point microprocessor (PXA270), 64 MB SDRAM, and 16 MB NOR FLASH. A Crossbow TelosB mote isconnected to the camera board to enable wireless communication, with amaximum data rate of 250 Kbps. The TelosB utilizes a Texas InstrumentsMSP430 micro-controller and an IEEE 802.15.4-compliant radio (ChipconCC2420), which are components of choice due to their low-poweroperation. The low power requirements and small size of the embeddedsmart camera make it an ideal choice for a wearable fall detector.

Histogram of Oriented Gradients (HOG) is a powerful image featureextraction method introduced by Dalai and Triggs. It is a lightweightalgorithm that requires reduced computations, as compared to thestate-of-the-art feature descriptors such as Haar wavelets, PCA-SIFTdescriptors, and Shape Contexts. This made it suitable for our proposedmethod implemented on an embedded platform.

The main goal of the HOG algorithm is to compute and extract localizedfeatures in the form of histograms of edge orientations. Since thealgorithm, as described in Dalal and Triggs, divides the image intoblocks and cells, it efficiently exploits the spatial properties withinthe image by concatenating the edge orientations in a series ofhistograms, according to the number of cells in a block. FIG. 12 aillustrates the division of an image into individual blocks and cells.The red and yellow squares represent blocks and cells, respectively.Although only two blocks are shown in the figure to make it lesscluttered, the number of blocks and cells can be de-fined by the userand depends on the type of application. Dalal and Triggs provide ananalysis on how the choices of blocks are made.

In one aspect of a method set forth herein HOG is employed as a scenedescriptor to detect gradual versus abrupt changes, and perform humanaction detection and classification on an embedded platform.Consequently, as opposed to the more common ways of using HOG thatrequire a high number of blocks and cells in order to detect/classifyobjects, we have determined that for the detection of changes, a reducednumber of blocks and cells is sufficient to accomplish the goal. As seenin FIG. 12 a, if we are not looking for a particular object covering asmaller area, using a large number of blocks and smaller cells wouldunnecessarily compromise the efficiency of the algorithm. Also, it canbe seen that most of the cells in FIG. 12 a will have a skeweddistribution of edge orientations. Thus, in our implementation, we useone block divided into nine cells, as depicted in FIG. 12( b), to detectthe changes in the edge orientations between different frames.

The HOG algorithm extracts edge orientation features from an image. Forthis purpose, the gradients in the vertical (dy) and horizontaldirections (dx) are computed at every pixel location within each cell.Once the edge orientation angle is computed (tan⁻¹(dy I dx)), it isplaced into a 9-bin histogram with a range from 0° to 180°. Every cellwill produce an edge orientation histogram and since there are 9 cellsin a block, the HOG block descriptor is composed of 9 concatenated cellhistograms. Since every histogram has nine bins, the HOG descriptor fora frame will be an 81-dimensional vector. The HOG block descriptor isused for scene description, and detecting gradual and abrupt changes asdescribed in Section 4.

Regarding Human Action Classification, various human actions can beclassified using methods set forth hereon. The system set forth hereinperforms fall detection. In the event of a fall, the system generates analarm requesting help from an external rescue entity (e.g. a hospital,9-1-1, family members). In addition to detecting falls, it can alsodetect and classify other human activities such as walking (which isconsidered default behavior), sitting, and lying down. Differentiatingthe actions of sitting and lying down from falling is also veryimportant to decrease false positives in fall detection. Section 4.1provides the algorithm used in the detection process. Additionally,experimental results in Section 5 demonstrate the robustness of thealgorithm against false alarms.

The classification algorithm is based on a correlation-baseddissimilarity scheme. Input to the classification stage is derived fromthe normalized version of the extracted HOG features, described inSection 3, which are 81-dimensional vectors. Given a reference vector(r) and measurement vector (s) both with N components, the dissimilaritydistance is computed using:

$\begin{matrix}{{{DD}_{rs} = {1 - \frac{\sum\limits_{i = 0}^{N - 1}\; {\left( {r_{i} - \overset{\_}{r}} \right)\left( {s_{i} - \overset{\_}{s}} \right)}}{\sqrt{\left\lbrack {\sum\limits_{i = 0}^{N - 1}\; {\left( {r_{i} - \overset{\_}{r}} \right)^{2}{\sum\limits_{i = o}^{N - 1}\; \left( {s_{i} - \overset{\_}{s}} \right)^{2}}}} \right\rbrack}}}}{where}\mspace{11mu} \; {{\overset{\_}{r} = {\sum\limits_{i = 0}^{N - 1}\; r_{i}}},{\overset{\_}{s} = {\sum\limits_{i = 0}^{N - 1}\; {s_{i}.}}}}} & (I)\end{matrix}$

Dissimilarity distance comparisons can be employed. To prevent falsepositives and distinguish between “falling”, “lying down”, and “sitting”actions, two different measures based on the correlation-baseddissimilarity distance (DD) are used.

Current frame versus “key frame” (DD¹ _(rs)) For this measure, wecalculate the DD between the current frame and the key frame. Initially,the key frame is set to be the first frame of the sequence. Since thesubject is moving (for instance can change rooms), this key frame needsto be updated. We perform the updates by looking at the variation ofcalculated DDs during last 15 frames. When the variation is small andthe distances are lower than a threshold, we update the key frame to bethe current frame.

FIG. 13 (top plot) shows the DD comparison between the current and keyframe. Since the microprocessor of the camera is a fixed-pointprocessor, everything is scaled by 100 to avoid floating pointoperations. In our experiments, the value of Da_(s) is used to signal anevent/action, i.e. either sitting, lying down or falling. Actionclassification is based on the value of DD² _(rs), as outlined below.

Current frame versus previous frame (Da_(s)): For this measure, wecalculate the DD between the current and the previous frame. This allowsus to differentiate between gradual and abrupt changes. For instance, asseen in FIG. 16( a), for the sitting action using only the DD¹ _(rs)measure would falsely trigger an alert. However, for sitting action, thechanges in edge directions are very gradual, and using the secondmeasure, DD² _(rs), allows us to correctly differentiate this actionfrom falling.

There is a strict set of logic, which governs the classification offalling, sitting, or lying down actions. The values of DD¹ _(rs) and DD²_(r), are compared with threshold values thr_event, thr_fall andthr_lying to set the appropriate event flags. These threshold values arecurrently determined based on the training experiments. We are workingon determining these values adaptively based on the recent history ofthe calculated dissimilarity distances. The logic rules used in oursystem is described in Algorithm 1. In our experiments, once a fall isdetected, a low-resolution version of the most recently captured imageand a fall flag are transmitted wirelessly to a computer. FIGS. 14(d)-(f) show the images transmitted from the camera.

Algorithm 1 (* Sets action flags based on dissimilarity distances *)  1.while new_frame  2. if DD_(rs) ¹ > thr_event  3. print(“Event Occured”) 4. if DD_(rs) ² > thr_fall  5. class_Flag ← 3  6. print(“Subject hasfallen”)  7. send(“fall Alarm”)  8. else if thr_lying < DD_(rs) ² <thr_fall  9. class_Flag ← 2 10. print(“Subject lay down”) 11. else ifDD_(rs) ² < thr_lying 12. class_Flag ← 1 13. print(“Subject sat down”)

Experiments were performed with two different subjects. Everything isrun on the microprocessor of the camera worn by the subjects. It takesbetween 58 and 64 ms to process a frame on the camera, i.e. theprocessing rate is between 15 and 17 frames per second. This includesgrabbing, buffering and HOG processing. FIG. 4 shows the humanactivities to be classified. FIGS. 14 (a)-(c) show the sitting, lyingdown and falling events from an external camera, while FIG. 14 (e)-(f)in the bottom row show the corresponding views from the embedded smartcamera worn by the subject. The HOG descriptors for frames belonging todifferent action scenarios (walking, sitting, lying down and falling)are displayed in FIG. 15.

For all the experiments, the values of thr_event, thr_fall andthr_laying are 60, 70 and 30, respectively. 16 trials and 10 trials ofthe fall event were performed with Subject 1 and Subject 2,respectively. Table 1 shows the accuracy of the system for detectingfalls. The system correctly detected the event of a fall with 93.75%accuracy for Subject 1, and 100% accuracy for Subject 2. In one trial,Subject 1 fell down very gradually (since it is hard to imitate anactual fall), and this is the reason of missing one fall event. Theoverall accuracy of fall detection for the 26 trials is 96.15%. Inaddition, 13 trials of lying down, and 12 trials of sitting wereperformed. Table 2 shows the accuracy of detecting sitting and lyingdown actions. The system detected the sitting and lying down actionswith 76.9% and 83.3% accuracy, respectively. The system did not generatea false positive alarm in any of the 25 trials with sitting and lyingdown. Lying down was misclassified as sitting twice, and sitting wasmisclassified as lying down once.

TABLE 1 Fall detection accuracy Fall Event Subject 1 subject 2Miss-classification 1  0 Correct-classification 15 10 Detection Rate93.75%  100%

TABLE 2 Accuracy of detecting actions of sitting and lying down SittingLying down Miss-classification 3 2 Correct-classification 10 10Detection Rate 76.92% 83.3%

The experimental results demonstrate the capabilities and the robustnessof the system in terms of correctly detecting falls, and classifyingcommon activities such as sitting, lying down and differentiating themfrom a fall event.

As expected edge orientations change significantly during/after falling(as seen in the camera view in FIG. 14 (f) compared to walking andsitting shown in FIG. 14( d). Differentiating between falling and lyingdown is a more challenging problem, since lying down also causessignificant changes in edge orientations. However, a fall event inducesa much more random and abrupt change than lying down and our DD² _(rs),measure allows us to differentiate these actions.

FIGS. 16( a) through 16(c) show the two different correlation-baseddissimilarity distances (DD¹ _(rs), and DD² _(rs)) calculated at everyframe. DD¹ _(rs) serves as a trigger for any event (i.e. sitting, lyingdown, or falling), while the value of DD² _(rs) differentiates sittingand lying down from falling.

According to the decision logic outlined herein, to declare a fall, boththe DD¹ _(rs) and DD² _(rs) should be higher than correspondingthresholds. FIG. 16( c) shows the values of DD¹ _(rs) and DD² _(rs) and(in blue and green, respectively) before, during and after a fall event.As can be seen, both measures exceed the thresholds. In contrast, thevalue of DD² _(rs) does not exceed the threshold level for sitting andlying down actions, despite the DD¹ _(rs) threshold levels beingexceeded. In fact the plot of DD² _(rs) values are very stable, andchanges are gradual for these actions. Thus using the two differentdistance measures described in Section 4.1 makes the system more robustagainst false positives. Moreover, using the level of DD² _(rs), thesystem can differentiate between sitting, lying down and falling.

There is set forth herein an approach for detecting falls, as well asdistinguishing between the actions of sitting and lying down by using awearable wireless embedded smart camera. Since the camera is wearable,the subject can be monitored wherever she/he may go including outdoors.Thus, contrary to other status sensor-based approaches, fall detectionis not limited to areas where the sensors are installed. In addition,contrary to static cameras monitoring the subjects, this wearable cameradoes not point towards the subject. Hence, the captured frames are theimages of the surroundings and do not violate the subject's privacy. Incase of a fall, an appropriate message can be sent to the emergencyresponse personnel via e-mail, with an attached image from the subject'scamera. This image of the surroundings aids in locating the subject.

Another aspect of the proposed approach is employing histograms oforiented gradients as a scene descriptor to detect gradual versus abruptchanges, and performing fall detection and differentiating betweennormal activities, such as walking, sitting and lying in bed, on anembedded platform. This approach uses a correlation-based dissimilaritydistance for distinguishing among different human activities. Thisentire approach has been implemented on an embedded smart camera that isworn by the subject. Image features are computed in real-time.

The presented results demonstrate the success of the proposed method indetecting falls. In case of a fall, the system captures and sends imagesvia e-mail for easier localization of the subject by emergency responseteams. In our experiments with two different subjects, we were able toget 96.15% accuracy for fall detection over 26 trials. Also, the systemdetected the sitting and lying down actions with 76.9% and 83.3%accuracy, respectively. The system did not generate a false positivealarm in any of the 25 trials with sitting and lying down.

End of Example 1 Example 2

About one-third of adults in the U.S. aged 65 or older fall every year,with 20% of the reported fall cases needing prompt medical attention.The methods that have been proposed for fall detection in recent yearspresent trade-offs between level of intrusiveness, coverage area,processing power requirements and detection accuracy. We present arobust and resource-efficient method for fall detection by using awearable embedded smart camera, which is a small, battery-operated unit.The proposed approach employs histograms of edge orientations as well asedge strength values, and analyzes their correlation. Moreover, weadaptively determine the cells that do not contribute to overall edgeinformation, and remove them autonomously. Since the camera is worn bythe subject, monitoring can continue wherever the subject may goincluding outdoors. The captured frames are not the images of thesubject, and this alleviates the privacy concerns. The alert and animage of the surroundings can be transmitted wirelessly, only when afall event is detected, for easier localization of the subject byemergency response teams. The experimental results obtained with over300 trials are very promising with a 91% detection rate for falls.

Falls among the elderly are major concern for both families and medicalprofessionals, since falls are considered to be the eighth leading causeof death in the U.S. Untreated fall injuries in adults 65 or older canresult in serious health complications, since 20% of all falls requireimmediate medical attention and about one-tenth of the falls result infractures. According to the U.S. census data, the number of elderlyadults over 65 will rise to 20% by 2030 (from 12.9% in 2009), due toincreasing life expectancy and a dropping fertility rate.

Since treatment after a fall is a very time-sensitive matter, falldetection becomes very important to minimize the adverse effects offalls, especially for elderly people living by themselves. Even thoughseveral user-activated commercial devices are available, they havelimited benefits, especially in situations where the user losesconsciousness. In response to growing needs, a new research field ofautonomous fall detection via dedicated signal processing devices hasevolved. Current fall-detection research can be grouped into three maincategories (with many devices using multiple methods at once to achievea higher detection accuracy).

Gyroscope/Accelerometer-based systems use wearable devices containing anaccelerometer, the output of which is used to detect a fall. A number ofapproaches are described for minimizing the false-alarm rate, includingwatching for no-movement and statistical models. The hardware variesfrom dedicated devices to commonly-available hardware (e.g.smartphones).

Acoustic/Vibration-based approaches employ sensor nodes that monitor forfloor vibrations or sounds, correlating them to specific events (e.g.walking, falling). This approach increases patient compliance, is lessintrusive, and can be installed in any environment without sacrificingits effectiveness.

Stationary camera-based systems monitor people from a stationary videocamera, whose output is processed by a dedicated computer. Mostapproaches use raw video data, while others address the concerns ofprivacy by using infrared or contrast-detection cameras. Stereoscopicvision and 3D scene reconstruction are other variations that aim toincrease system accuracy.

However, both the stationary-camera and vibration-based approaches arelimited to the areas where the sensors are installed. There is set forthherein an efficient method to detects falls by using a wearable wirelessembedded smart camera. Since the camera is wearable, the subject can bemonitored wherever she/he may go including outdoors. Thus, contrary toother static sensor-based approaches, fall detection is not limited toareas where the sensors are installed. Our approach to fall detectionalso aims to eliminate privacy concerns. As opposed to static camerasthat watch the subjects, this wearable smart camera does not pointtowards the subject. Moreover, the frames are not transmitted toanywhere, but processed onboard by the microprocessor. Only when a falloccurs, an appropriate message can be sent wirelessly to the emergencyresponse personnel, optionally including an image from the subject'scamera. This image of the surroundings can aid in locating the subject.

The approach set forth herein is based on the oriented image gradients.In our method, there are major differences from the Histogram ofOriented Gradients (HOG) introduced by Dalal and Triggs. First, we buildseparate histograms for gradient orientations and gradient strengths,and then find the correlation between them. Another difference is thatwe do not use a constant number of cells in a block. We adaptivelydetermine the cells that do not contribute to overall edge information,and remove them autonomously. As will be shown by experimental results,the proposed method is more robust compared to using fixed number ofcells in detecting falls. We implemented this algorithm on a wearableembedded smart camera, which is a small, stand-alone, battery-operatedunit.

The algorithm is implemented on a CITRIC mote, which features a 624 MHzfixed-point microprocessor, 64 MB SDRAM, and 16 MB NOR FLASH. Thewireless transmission of data is performed by a Crossbow TelosB mote.

Histogram of Oriented Gradients (HOG) provides a powerful and efficientmethod for image feature extraction. Compared to other featuredescriptors such as Haar wavelets, PCA-SIFT descriptors and ShapeContexts, HOG is computationally less expensive, making it more suitablefor embedded camera platforms that have limited memory and processingpower.

In the HOG algorithm, the image is divided into blocks and each block isdivided into η cells, as shown in FIG. 17. For each cell, an m-binhistogram of gradient orientations is built. The magnitude and theorientation of the gradient are calculated at each pixel. Each gradienthas a vote in its bin, which is its magnitude. The combination of nhistograms forms the HOG descriptor, with the size of m×n entries.

There is utilized a modified descriptor, which is different from HOG, asexplained below.

Modified Descriptor

In the method set forth herein, different from the HOG, there isutilized separate histograms for gradient orientations and gradientstrengths, and then find the correlation between them. During a fall,edge orientations change significantly, which is reflected in thegradient orientation histograms. Also, since falls are relatively fastevents, the edges in images get blurred. This is captured by the changein the gradient strength histograms. We have seen in our experimentsthat using original HOG can create false positives while walking. Inaddition, we do not use a fixed number of cells in each block. Rather,we adaptively determine the cells that do not contribute to overall edgeinformation, and remove them autonomously.

There is employed gradient orientation and strength histograms to detectgradual versus abrupt changes on an embedded platform. It has beendetermined that for the detection of changes, a reduced number of blocksis sufficient. In order to lighten the processing load of the embeddedcamera, our implementation only uses one block that is initially dividedinto 16 cells, as including larger number of blocks would unnecessarilycompromise the efficiency.

To build the histograms, horizontal (dx) and vertical (dy) gradients arecomputed first for every pixel within a cell. Then these values are usedto calculate the gradient orientation (tan⁻¹(dy/dx)) and the gradientstrength (₁,/dx²+dy²) at each pixel.

As indicated above, in the original HOG algorithm, the orientationvalues are placed in a 9-bin histogram (with range 00 to 180°) using avoting mechanism based on the gradient strength. This causes falsealarms in some cases. An example is seen in FIG. 18, where the falloccurs between frames 50 and 60, yet walking triggers a false “fall”alarm). Another example is shown in FIG. 19( a), where ‘lying down’ and‘sitting’ were classified as a fall with the original HOG.

In the method set forth herein there is utilized a separate 9-binhistogram for gradient strength values. The range of these is from 0 to√{square root over (255²+255²)}≈361. However, experimentally the maximumvalue detected was approximately 260, which was the value used for therange in order to avoid skewing the histogram toward lower values. Inour implementation, since every histogram consists of 9 bins and thereare at most 16 cells in a block, the HOG descriptor of a frame consistsof two 144-dimensional vectors: one containing the concatenatedhistograms for edge orientations (BO) and another containing theconcatenated histograms for edge strengths (ES).

There is also employed an adaptive change in the number of cells in theblock, and this will be described in Section II-C.

Fall Detection

The correlation-based dissimilarity scheme is used as the basis of thedetection algorithm. Once the extracted feature histograms EP and ES(described in Sec. II-A) re normalized, the dissimilarity distancebetween the current frame at time t (measurement vector s) and theprevious frame (t-1) (reference vector r) is computed for both the edgestrength (ES) and orientation (EO) histograms using equation by using:

$\begin{matrix}{{{DRS} = {1 - \frac{\sum\limits_{i = 0}^{N - 1}\; {\left( {r_{i} - \overset{\_}{r}} \right)\left( {s_{i} - \overset{\_}{s}} \right)}}{\sqrt{\left\lbrack {\sum\limits_{i = 0}^{N - 1}\; {\left( {r_{i} - \overset{\_}{r}} \right)^{2}{\sum\limits_{i = o}^{N - 1}\; \left( {s_{i} - \overset{\_}{s}} \right)^{2}}}} \right\rbrack}}}}{{\overset{\_}{r} = {\sum\limits_{i = 0}^{N - 1}\; \left( r_{i} \right)}},{\overset{\_}{s} = {\sum\limits_{i = 0}^{N - 1}\; \left( s_{i} \right)}}}} & (I)\end{matrix}$

Dissimilarity distance values for ED (D_(ES)) and EO (D_(EO)) arecross-related, which attenuates the noise in the signal and emphasizesthe peaks. To increase the robustness, the attenuated signal isautocorrelated ((D_(ES)D_(EO))²). The result of this operation is shownin FIG. 23( d).

Once D_(ES) and D_(EO) are cross-correlated, followed by autocorrelationof the resulting signal. the gradual motion of the subject (i.e.walking. lying. sitting) is significantly attenuated, which provides aclear peak corresponding to the “fall” event.

In order to distinguish between the gradual motion of walking, sitting,lying and the abruptness of a fall, a threshold of T_(d)=50% is set.Once the camera detects that this threshold has been exceeded, a ‘fall’flag is triggered. Experimentally, it has been determined that the peaksfor gradual motion do not exceed the 50% threshold, as the originalsignals are attenuated by more than two-thirds.

Adaptive Number of Cells

There is set forth a mechanism that adaptively controls the number ofcells to be used for the feature descriptor according to their content.The motivation is that cells containing no edges or edges with lowstrength do not contribute to the scene information, and increase thesimilarity score between concatenated histograms. FIG. 20 illustrates ascenario for a fall event, wherein the camera points to a table. As canbe seen, cells 1, 2, 5, 6, 9, 10, 13, and 14 add minimal or no usefulinformation to detect the fall or differentiate it from walking.Including the histograms for these cells in the feature descriptor willresult in lower dissimilarity scores after using (1).

FIGS. 21( a) and 21(b) are the histograms of edge orientations beforeand after a fall, respectively, obtained by using a fixed number ofcells. The adjusted histograms obtained by removing the leastcontributing cells with the proposed method are shown in FIGS. 21( c)and 21(d). The dissimilarity distance between the histograms in FIGS.21( a) and 21(b) is 0.866. On the other hand, if we remove thehistograms of cells with the least contribution (circled in FIG. R21(a))from the feature vector, the dissimilarity distance increases to 1.024.

Another supporting example can be seen by comparing Fig. PPb and PPc.The amplitude of the peak for dissimilarity in a falling event is higherwhen using an adaptive number of cells (FIG. 19( c)). Having a higherdissimilarity distance between falling and previous states contributesto the robustness of the system to reliably detect fall events.Consequently, the system is less prone to false negatives. i.e. missing‘fall’ events. More results comparing adaptive number of cells withfixed number of cells are presented in Sec. III.

To determine which cells to remove, the maximum amplitude among the binswithin a cell is found first. Then, we calculate the mean value and thestandard deviation of the vector of maximums from the n cells in aframe. Finally, the algorithm removes the cells whose maximum value area standard deviation away from the computed mean. Thus, not only thenumber of removed cells is adaptive, but also the threshold is adaptedaccording to the cell content within current frame at time t. To avoidpossible introduction of false positives by discarding too many cells,the algorithm is designed to remove a maximum of 8 cells (half of thetotal number of cells).

To test the propose system, there was conducted over 600 trials withthree different subjects. Subjects wore the embedded smart camera ontheir belts, and they fell, sat down or lied down in their own way. Theproposed adaptive method was tested with 330 trials (110 falls, 110sitting, 110 lying down). There was also performed additional 330 trialsby using a fixed number of cells to compare the performances. FIGS. 6(a) and 6(b) show example photos taken of a subject during two falltrials. It should be noted that these are not from the camera worn bythe subject. The images seen by the embedded smart camera attached tothe subject's waist can be seen in FIG. 24( a) through 24(d) and 26(a)through 26(d).

All the results were obtained by using the same parameter values for alltrials of sitting, lying down and falling. More specifically, we usedone block, 16 for the initial number of cells, τ_(d)=0.5 for fallthreshold, and α2=0.5 for the standard deviation distance.

As seen in Table I, out of 110 falls, the fall detection rate obtainedby using adaptive number of cells is 91%, which is significantly betterthan the 48.2% that is obtained when a fixed number of cells is used.The system was able to reliably detect falls from the ‘stand up’position as well as falls from the ‘lying down’position (i.e. falls froma bed surface). The main reason behind the false negatives is thecautiousness and fear of subjects when they are imitating a fall. Evenwith cushions and other safety precautions in place, we found that mostsubjects are too afraid to “actually fall”. In our experiments, weobserved that all the false negatives occurred when the subjects werefalling directly to their site in a gradual manner in an effort toprotect themselves. In an actual fall, this will not be the case.

TABLE I Detection rate on 220 fall trials (FN denotes False Negatives)Correct Fall Detection Classification FN Rate Fixed (110) 53 57 48.2%Adaptive (110) 100 10 91%  

FIGS. 23( a) through 23(d) show graphs of D_(EO), D_(ES), D_(EO)×D_(ES)and (D_(EO)×D_(ES))², respectively, during events of falling, lying downand sitting. These illustrate the robustness of the system indifferentiating a fall from other actions.

As seen in FIG. 24( a) through 24(c), during a fall, in addition to edgelocations, edge strengths (ES) changes as well due to the blurriness ofthe captured image. There is a significant peak in the value of D_(ES)caused by the fall. The edge strength values corresponding to the framesgiven in FIG. 24( a) and FIG. 24( c) are shown in FIG. 25( a) and FIG.25( b), respectively. As can be seen, during the fall, the edge strengthvalues decrease significantly.

Example frames captured by the camera during fall and sitting events areshown in FIG. 24( a) through 24(d) and FIG. 26( a) through 26(d),respectively.

Table II summarizes the false positive rates, when using a fixed numberof cells and the proposed method in 440 trials. There were 220 trials ofsitting, and 220 trials of lying down. The false positive rates whenusing an adaptive number of cells, and the fixed number of cells are11.36% and 10.45%, respectively. The reason of this slight increase hasbeen observed as follows: Since the current version of our code is notfully optimized, we have observed that in some of these trials, theprocessing of a frame takes more than 100 msec when determining whichcells to use adaptively and building histogram vectors accordingly. Thisin turn causes dropping more frames than usual and making theconsecutive frames further apart from each other, which increases thedissimilarity. With the current state of code, the processing time of aframe is 79 msec on the average, and about 50 msec of this time is onlyto grab the frame. However, after decreasing the grabbing time, andoptimizing the code, we do not anticipate false positives caused by theprocessing time.

There is presented an approach for detecting falls by a wearableembedded smart camera with limited memory and processing power. Sincethe camera is wearable, the subject can be monitored wherever she/he maygo including outdoors. Thus, contrary to other static sensor-basedapproaches, fall detection is not limited to areas where the sensors areinstalled. In addition, the wearable camera does not point towards thesubject; the images are processed onboard, and are not transmittedanywhere. Thus, the system preserves the subjects privacy. Only when afall occurs, an appropriate message can be sent wirelessly to theemergency response personnel, optionally including an image from thesubject's camera. This image of the surroundings can aid in locating thesubject.

The presented results obtained with over 600 trials of sitting, lyingdown and falling demonstrate the success of the proposed method. Thedetection rate for falls is 91%, and the false positive rate is 11.36%.We have observed that the reason of some of the false positives is theprocessing time, and they happen when the processing of a frame takesmore than 100 msec. Currently, the code is not fully optimized and theprocessing time of a frame is 79 msec on the average. About 50 msec ofthis time is only to grab the frame. However, after decreasing thegrabbing time, and optimizing the code, we anticipate decreasing falsepositives caused by the processing time.

TABLE II False positive (FP) rates on 440 trials of sitting and lyingdown FP Overall FP Action FP rate (%) rate (%) Fixed(220) Sit (110) 87.27% 10.45% Lay(110) 15 13.63% Adaptive(220) Sit (110) 8 7.27% 11.36%Lay(110) 17 15.45%

End of Example 2

A small sample of apparatus systems and methods set forth herein includethe following:

A1. A camera device comprising: an image sensor; a memory; a processorfor processing images; wherein the camera device is adapted to bewearable by a human subject in a manner that images captured using thecamera device represent surroundings of the human subject; wherein thecamera device is operative to process images captured using the cameradevice for detection of an event, the event being an action of the humansubject, the event being detected by performance of an image processingmethod that includes a comparison of a subsequently captured image to anearlier captured image; wherein the camera device is operative towirelessly transmit a message to an external destination responsively tothe detection by the camera device of the event. A2. The camera deviceof A1, wherein the certain event is a fall. A3. The camera device of A1,wherein the camera device is operative to discriminate between a fall bya subject and a sitting down by a subject. A4. The camera device of A1,wherein the camera device is operative to discriminate between a fall bya subject and a laying down by a subject. A5. The camera device of A1,wherein the message includes one or image representing surroundings ofthe subject. A6. The camera device of A1, wherein the method includesdeveloping a histogram of edge orientations of an image. A7. The cameradevice of A1, wherein the event is a laying down of the human subject.A8. The camera device of A1, wherein the event is one or more of alaying down event or a sitting down event of the human subject, andwherein the camera device utilizes the one or more of a laying downevent or a sitting down event to determine whether the human subject hasbecome ill. A9. The camera device of A1, wherein an image processingrate of the processor is restricted from being slower than a frame rateof the camera device. A10. The camera device of A1, wherein an imageprocessing rate of the processor is restricted from being less than 50percent of a frame rate of the camera device. All. The camera device ofA1, wherein the camera device is restricted from transmitting an imageto an external destination unless an event is detected by the cameradevice. A12. The camera device of A12, wherein a transmitted imagepermitted to be transmitted from the camera device to the externaldestination is devoid of a representation of the human subject.B1. A method comprising: positioning a camera device on a human subjectin a manner that the camera device is directed away from the humansubject so that images captured using the camera device representsurroundings of the human subject, the camera device having an imagesensor, a memory and a processor; and processing images captured usingthe camera device to detect an occurrence of an event, the event beingan action of the human subject, the processing including comparing asubsequent captured image to a prior image. B2. The method of B1,wherein the event is a fall. B3. The method of B1, wherein theprocessing includes developing a histogram of edge orientations of animage. B4. The method of B1, wherein the action is a fall, and whereinthe method includes wirelessly transmitting a message to an externaldestination responsively to the fall being detected. B5. The method ofB1, wherein the message includes an image representing surroundings ofthe human subject. B7. The method of B1, wherein the event is a layingdown of the human subject, and wherein the method includes utilizing alaying down event for determination of whether the human subject hasbecome ill. B8. The method of B1, wherein the processing includesdetermining that the human subject has become ill based on or more of aduration and a count of a laying down event. B9. The method of B1,wherein the processing includes determining that the human subject hasbecome ill responsively to a count of laying down events exceeds athreshold during a predetermined time window. B10. The method of B9,wherein the processing includes determining that the human subject hasbecome ill further responsively to a duration of a laying down event.B11. The method of B1, wherein the processing includes processing ofimages devoid of a representation of a human subject on which the cameradevice is positioned. B12. The method of B1, wherein the processingincludes processing of images captured while the human subject isinternal of a building and processing of images captured while the humansubject is external of a building. B13. The method of B1, whereinresponsively to the processing the camera device outputs an indicatorobservable by the human subject. B14. The method of B1, whereinresponsively to the processing the camera device outputs an indicatorobservable by the human subject and transmits a message to an externaldestination. B15. The method of B1, wherein responsively to a layingdown event being detected by the processing the camera device outputs anindicator observable by the human subject and transmits a message to anexternal destination indicating that the human subject has become ill,wherein the indicator observable by the human subject includes a tactileindicator and audible indicator. B16. The method of B1, whereinresponsively to determination that an activity level of the humansubject has exceeded a desirable level by the processing the cameradevice outputs an indicator observable by the human subject promptingthe human subject to reduce the human subject's activity level.C1. A computer program product for detecting action of a human subject,the computer program product comprising: a computer readable storagemedium readable by a processing circuit and storing instructions forexecution by the processing circuit for performing a method comprising:processing, by a processor, images representing surroundings of a humansubject; determining, by the processor, responsively to the processingan action of the human subject, wherein the processing includescomparing a subsequently captured image to a prior captured image. C2.The computer program product of C1, wherein the event is a fall. C3. Thecomputer program product of C1, wherein processing includes developing ahistogram of edge orientations of an image. C4. The computer programproduct of C1, wherein the method includes wirelessly transmitting amessage to an external destination responsively to the fall beingdetected. C5. The computer program product of C4, wherein the messageincludes an image representing the surroundings of the human subject.C6. The computer program product of C1, wherein the method includesoutputting responsively to the determining an indicator observable bythe human subject and transmitting to an external destination a message.C7. The computer program product of C1, wherein the wherein the methodincludes restricting transmitting of an image from a camera device to anexternal destination unless an event is detected by the camera device.

While the present invention has been described with reference to anumber of specific embodiments, it will be understood that the truespirit and scope of the invention should be determined only with respectto claims that can be supported by the present specification. Further,while in numerous cases herein wherein systems and apparatuses andmethods are described as having a certain number of elements it will beunderstood that such systems, apparatuses and methods can be practicedwith fewer than or greater than the mentioned certain number ofelements.

What is claimed is:
 1. A camera device comprising: an image sensor; amemory; a processor for processing images; wherein the camera device isadapted to be wearable by a human subject in a manner that imagescaptured using the camera device represent surroundings of the humansubject; wherein the camera device is operative to process imagescaptured using the camera device for detection of an event, the eventbeing an action of the human subject, the event being detected byperformance of an image processing method that includes a comparison ofa subsequently captured image to an earlier captured image; wherein thecamera device is operative to wirelessly transmit a message to anexternal destination responsively to the detection by the camera deviceof the event.
 2. The camera device of claim 1, wherein the messageincludes one or image representing surroundings of the subject.
 3. Thecamera device of claim 1, wherein the event is a laying down of thehuman subject.
 4. The camera device of claim 1, wherein the event is oneor more of a laying down event or a sitting down event of the humansubject, and wherein the camera device utilizes the one or more of alaying down event or a sitting down event to determine whether the humansubject has become ill.
 5. The camera device of claim 1, wherein animage processing rate of the processor is restricted from being lessthan 50 percent of a frame rate of the camera device.
 6. The cameradevice of claim 1, wherein the camera device is restricted fromtransmitting an image to an external destination unless an event isdetected by the camera device.
 7. A method comprising: positioning acamera device on a human subject in a manner that the camera device isdirected away from the human subject so that images captured using thecamera device represent surroundings of the human subject, the cameradevice having an image sensor, a memory and a processor; and processingimages captured using the camera device to detect an occurrence of anevent, the event being an action of the human subject, the processingincluding comparing a subsequent captured image to a prior image.
 8. Themethod of claim 7, wherein the event is a fall.
 9. The method claim 7,wherein the processing includes developing a histogram of edgeorientations of an image.
 10. The method of claim 7, wherein the actionis a fall, and wherein the method includes wirelessly transmitting amessage to an external destination responsively to the fall beingdetected.
 11. The method of claim 7, wherein the message includes animage representing surroundings of the human subject.
 12. The method ofclaim 7, wherein the event is a laying down of the human subject, andwherein the method includes utilizing a laying down event fordetermination of whether the human subject has become ill.
 13. Themethod of claim 7, wherein the processing includes determining that thehuman subject has become ill responsively to a count of laying downevents exceeds a threshold during a predetermined time window.
 14. Themethod of claim 13, wherein the processing includes determining that thehuman subject has become ill further responsively to a duration of alaying down event.
 15. The method of claim 7, wherein the processingincludes processing of images devoid of a representation of a humansubject on which the camera device is positioned.
 16. The method ofclaim 7, wherein the processing includes processing of images capturedwhile the human subject is internal of a building and processing ofimages captured while the human subject is external of a building. 17.The method of claim 7, wherein responsively to the processing the cameradevice outputs an indicator observable by the human subject.
 18. Themethod of claim 7, wherein responsively to the processing the cameradevice outputs an indicator observable by the human subject andtransmits a message to an external destination.
 19. The method of claim7, wherein responsively to a laying down event being detected by theprocessing the camera device outputs an indicator observable by thehuman subject and transmits a message to an external destinationindicating that the human subject has become ill, wherein the indicatorobservable by the human subject includes a tactile indicator and audibleindicator.
 20. The method of claim 7, wherein responsively todetermination that an activity level of the human subject has exceeded adesirable level by the processing the camera device outputs an indicatorobservable by the human subject prompting the human subject to reducethe human subject's activity level.
 21. A computer program product fordetecting action of a human subject, the computer program productcomprising: a computer readable storage medium readable by a processingcircuit and storing instructions for execution by the processing circuitfor performing a method comprising: processing, by a processor, imagesrepresenting surroundings of a human subject; determining, by theprocessor, responsively to the processing an action of the humansubject, wherein the processing includes comparing a subsequentlycaptured image to a prior captured image.
 22. The computer programproduct of claim 21, wherein the method includes wirelessly transmittinga message to an external destination responsively to the fall beingdetected.
 23. The computer program product of claim 21, wherein themessage includes an image representing the surroundings of the humansubject.
 24. The computer program product of claim 21, wherein themethod includes outputting responsively to the determining an indicatorobservable by the human subject and transmitting to an externaldestination a message.
 25. The computer program product of claim 21,wherein the wherein the method includes restricting transmitting of animage from a camera device to an external destination unless an event isdetected by the camera device.